1. Field of the Invention
The present invention is directed to an engine drive assembly, and in particular, to a motorcycle drive assembly crankcase having increased volume and adaptability to mount to different transmissions and to route oil lines differently so as to correspond to the paths required for the transmission.
2. Prior Art
A drive assembly that includes an engine providing power and a transmission providing torque and speed adjustment to the rear wheel, which powers motorcycles. Motorcycle engines typically include a crankcase upon which is mounted the cylinders and the pistons as well as housing the flywheel and supporting the crankshaft as part of a crankcase assembly. The crankcase also defines a camchest housing the engine cams.
The crankcase assembly mounts at its rear to a transmission case or housing and provides drive to the rear wheel through the crankshaft driving a belt, chain or drive shaft. Mounting between the crankcase and the transmission case may have several configurations. In one common configuration, the transmission and the crankcase mount together with generally horizontal pads that overlap one another at the rear of the crankcase and front of the transmission case. More recently, the crankcase and transmission are configured wherein the crankcase and transmission housing mount along a generally vertical interface that lessens the tendency of the transmission and crankcase to slide relative to one another.
In addition to powering the drive train, the crankcase may provide circulation of lubricants to an oil reservoir with an oil pump mounted to the crankcase. Prior drive assembly designs that utilize a vertical interface defined a cavity at one side and utilized oil hoses extending from the crankcase into the cavity and coupling to the transmission for circulation to and from the oil reservoir. The cavity was needed to provide sufficient space for routing of such hoses, but needed a cover to protect the oil lines. However, these oil lines require a preformed right angle bend, are expensive and difficult to install. The transmission housing of other drive assemblies includes an associated oil reservoir, often mounted at the bottom of the transmission housing. This configuration required long hoses or a complicated routing system through the transmission housing itself, requiring special machining. Still other designs include remote oil reservoirs and some may utilize portions of the motorcycle frame as a reservoir.
The engines and transmissions of the prior art are dedicated so that the transmissions and engines of one system cannot be interchanged with those of another having a different style. As motorcycles often have performance modifications made to them, a dedicated mounting arrangement is a disadvantage to those who wish to improve the performance of their motorcycle and upgrade either their engine and/or their transmission, as the choices are limited by the mounting interface. Heretofore, it has not been possible to easily mix and match transmissions and crankcases.
It can be seen that a new and improved motorcycle drive assembly is needed. Such a drive assembly includes a crankcase that should provide for mounting to transmissions having different mounting interfaces. In addition, such engines should minimize the outer cavities that are formed in the crankcase found in the prior art and increase the volume of the camchest portion of the casing. Moreover, such a crankcase should provide fittings and routing so that oil may be routed easily to reservoirs for different style transmissions with different mounting interfaces. Such a crankcase should also provide for improved air-cooling with more air circulation between the transmission and the engine crankcase. The present invention addresses these as well as other problems associated with motorcycle drive assemblies.